A typical air core gauge comprises a magnetic rotor, two or more coils wound around the magnetic rotor, a spindle attached to the shaft of the magnetic rotor and a pointer tip on the end of the spindle. The magnetic rotor is pivotally mounted within the coils, to which an electric current is applied. When the electric current is applied to the coils, the coils generate a magnetic flux that acts upon the magnetic rotor causing rotation of the rotor until the rotor is aligned with the composite magnetic vector generated by the coils. The magnetic rotor causes the spindle to rotate, in turn rotating the pointer, which is used as a gauge to display information.
Typically, a metal shield surrounds the coil and magnet assembly to prevent external fields from disrupting the magnetic vector created by the coils. This metal shield may be referred to as the "can". In operation of the gauge, the can exhibits a slight residual magnetic field that affects the pointer deflection angle causing a magnetic hysteresis. Air core gauges also have a mechanical hysteresis that affects the gauge operation, but which is reduced by normal driving vibrations in the vehicle. The magnetic hysteresis in the can resists changes to the magnetic field created by the coils, thus affecting the resultant magnetic vector to which the rotor aligns itself and thus causing positional error in the pointer of the gauge.